So far, catechins have been reported to have a suppressing effect on an increase in cholesterol level and an inhibitory effect on α-amylase activity (see, for example, JP-A-60-156614 and JP-A-03-133928). For such physiological effects to manifest, it is necessary for an adult to drink 4 to 5 cups of tea a day. Accordingly, there has been a demand for techniques enabling catechins to be contained catechins at high concentration in beverages to facilitate the ingestion of a large amount of catechins. As one of such techniques, catechins are added in a dissolved form to a beverage by using the concentrate of a tea extract (see, for example, JP-A-59-219384).
So-called non-polymer catechingallates such as gallocatechingallate and epigallocatechingallate are known to be particularly high in physiological activities, among such non-polymer catechins, and their use as antiallergic agents or cerebral function activators in the field of foods, beverages and health foods has been proposed (see, for example, JP-A-08-242813, and JP-A-11-18722). However, these non-polymer catechingallates are obtained through many purification processes, in which they are exposed to an acid, an alkali, heat, a solvent and the like, respectively, in the course of their production in which they are highly purified and formulated into preparations to enhance their physiological effects. As a result, these non-polymer catechingallates show a unique color tone while they are green tea extracts. Therefore, there has been a serious problem in that difficulties are encountered in making full use of these non-polymer catechingallates upon formulation of beverages despite their high physiological effects. For beverages containing such non-polymer catechingallates added at high concentration, the stability in their external appearance against pH variations during long-term storage or upon heat sterilization has thus become a particularly important goal to be achieved.
In addition, the unique color tone of such non-polymer catechingallates involves another problem in that, upon taking the beverages, the pigmentation of teeth tends to become readily recognizable.